OSX - Sometimes C.hid_read returns all zeros

[chillyvee]

On a Mac M1(and x64), especially with Ledger Nano X:

The function call at line 216: https://github.com/Zondax/hid/blob/master/hid_enabled.go#L216

// Execute the read operation
	read := int(C.hid_read(device, (*C.uchar)(&b[0]), C.size_t(len(b))))

Sometimes returns read == 64, and a zero filled buffer
C.hid_read [64] => [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]

This is most commonly seen during a sign request : INS_GET_ADDR_SECP256K1

Where:

• the Command is fully sent, a success 0x9000 is received
• the first return packet is 64 bytes of 0x00
• the second return packet is the tail of the signature with sequenceIdx == 1 (causing the front part of the signature to be missing)

This error occurs "randomly" from time to time.

We can also share that at this point of the program:
https://github.com/Zondax/hid/blob/master/hidapi/mac/hid.c#L802

/* Helper function, so that this isn't duplicated in hid_read(). */
static int return_data(hid_device *dev, unsigned char *data, size_t length)
{
	/* Copy the data out of the linked list item (rpt) into the
	   return buffer (data), and delete the liked list item. */
	struct input_report *rpt = dev->input_reports;
	size_t len = (length < rpt->len)? length: rpt->len;
	memcpy(data, rpt->data, len);  <------- HERE rpt->data = [0,0,0,0,0,0,.....0,0]

The contents of rpt->data are all 0x00

Checking the event source:
hid_report_callback
https://github.com/Zondax/hid/blob/master/hidapi/mac/hid.c#L566

/* The Run Loop calls this function for each input report received.
   This function puts the data into a linked list to be picked up by
   hid_read(). */
static void hid_report_callback(void *context, IOReturn result, void *sender,
                         IOHIDReportType report_type, uint32_t report_id,
                         uint8_t *report, CFIndex report_length)
{
	struct input_report *rpt;
	hid_device *dev = context;

	/* Make a new Input Report object */
	rpt = calloc(1, sizeof(struct input_report));
	rpt->data = calloc(1, report_length);
	memcpy(rpt->data, report, report_length); <-----

The contents of rpt->data are all 0x00 at the source as well

Is it an OSX Bug? Why only on signature returns? Why do all other APDUs work without issue?

• Affects Big Sur (OS X 11) and Monterey (OS X 12)

Maybe it's a ledger-cosmos bug? But why does this APDU only fail on CLI and not Keplr (Browser extension)?

Maybe it's a NanoX+Cosmos Bug+CLI Bug? NanoSPlus doesn't experience this problem very often. Faster processor?

NanoX ledger-cosmos v2.34.3
NanoSPlus ledger-cosmos v2.34.3

This affects cosmos-sdk cli applications as documented here:
cosmos/ledger-cosmos#57